Findings: Noncontrast CT: The patient is status post right suboccipital craniotomy. There is a subtle area of hypoattenuation off-midline to the right, anterior and lateral to the pons.
Contrast enhanced CT demonstrates a subtle area of nonenhancing hypoattenuation off-midline to the right, anterior and lateral to the medulla.
MRI:
Sagittal T1-weighted FLAIR demonstrates expansion of the prepontine cistern, and enlargement of the CSF space anterior to the proximal cervical spinal cord and medulla, with displacement of the medulla posteriorly. This space contains an extra-axial mass, demonstrating heterogeneous signal intensity.
Coronal T2-weighted FLAIR demonstrates heterogeneous signal intensity in the prepontine cistern.
Axial T1 weighted images demonstrates the prepontine cistern extra-axial mass that is near CSF signal intensity with enlargement of the pre-medullary cistern.
Axial T2 weighted images demonstrates the lamellated mass, which is heterogenous in signal intensity posterior to the hypophsial fossa and anterior to the basilar artery.
Axial T1-weighted image with gadolinium demonstrates no significant enhancement of the extra-axial mass.
Axial Diffusion Weighted image demonstrate restricted diffusion.
Sagittal 3D FIESTA demonstrates low signal in the prepontine cistern, and enlargement of the CSF space anterior to the proximal cervical spinal cord and medulla.
Axial 3D FIESTA image demonstrates low signal intensity in the prepontine cistern, medial to cranial nerve V, and adjacent to the right cranial nerve VII and VIII complex.

Findings: Noncontrast CT: The patient is status post right suboccipital craniotomy. There is a subtle area of hypoattenuation off-midline to the right, anterior and lateral to the pons.
Contrast enhanced CT demonstrates a subtle area of nonenhancing hypoattenuation off-midline to the right, anterior and lateral to the medulla.
MRI:
Sagittal T1-weighted FLAIR demonstrates expansion of the prepontine cistern, and enlargement of the CSF space anterior to the proximal cervical spinal cord and medulla, with displacement of the medulla posteriorly. This space contains an extra-axial mass, demonstrating heterogeneous signal intensity.
Coronal T2-weighted FLAIR demonstrates heterogeneous signal intensity in the prepontine cistern.
Axial T1 weighted images demonstrates the prepontine cistern extra-axial mass that is near CSF signal intensity with enlargement of the pre-medullary cistern.
Axial T2 weighted images demonstrates the lamellated mass, which is heterogenous in signal intensity posterior to the hypophsial fossa and anterior to the basilar artery.
Axial T1-weighted image with gadolinium demonstrates no significant enhancement of the extra-axial mass.
Axial Diffusion Weighted image demonstrate restricted diffusion.
Sagittal 3D FIESTA demonstrates low signal in the prepontine cistern, and enlargement of the CSF space anterior to the proximal cervical spinal cord and medulla.
Axial 3D FIESTA image demonstrates low signal intensity in the prepontine cistern, medial to cranial nerve V, and adjacent to the right cranial nerve VII and VIII complex.